Self-hardening material and process for layerwise formation of models

ABSTRACT

The invention relates to a self-hardening material for layerwise construction of three-dimensional components, whereby the material comprises at least one particulate material and a separately applied bonding agent for bonding the particulate material, and has a setting time which is at least several times as long as the application time of a particulate layer.

CLAIM OF PRIORITY

The present application claims priority from German Application No. DE102006038858.5, filed on Aug. 20, 2006 and is the National Phase of PCTApplication PCT/DE2007/001372, filed on Aug. 6, 2007, disclosure ofwhich is hereby incorporated by reference herein.

FIELD OF THE INVENTION

This invention relates to a self-hardening material and a process forlayered formation of three-dimensional components.

BACKGROUND

The process for the formation of three-dimensional components has beenknown for a long time.

For example, European Patent EP 0 431 924 B1 describes a process for themanufacture of three-dimensional objects from computer data. Itdescribes a particulate material that can be deposited in a thin layeron a platform and selectively printed with a binder using a print head.The printed area is bonded and sets under the influence of the binder.The platform is lowered by the thickness of one layer and a new layer ofparticulate material is spread and is also bonded. These steps arerepeated until a given height is achieved. A three-dimensional object iscreated from the printed and bonded areas. The object, which is embeddedin loose particulate material, is released from the platform, thenremoved from the loose particulate material.

It is observed that objects formed by this process have been shown tohave poor dimensional stability due to uneven hardening and thereforethe tolerances in the formed components are relatively high.

SUMMARY OF THE INVENTION

Accordingly, pursuant to a first aspect of the present invention, thereis contemplated a self-hardening material for layerwise construction ofthree-dimensional components, whereby the material com-prises at leastone particulate material and a separately applied bonding agent forbonding the particulate material, and where the setting time is at leastseveral times as long as the application time of a particulate layer.

The invention of the first aspect may be further characterized by one orany combination of the features described herein, such as the settingtime is greater than 20 times as long as the application time of theparticulate layer; setting of the binding material takes place afterformation of the component; the component demonstrates uncured settingwithin 72 hours; the binder contains at least one component of the groupincluding acrylate, methacrylate and/or sterols; the particulatematerial used is polymethylmethacrylate; the binding material can bepolymerised using UV light, radiation, heat and/or reactive activators;the binder is composed of a multi-component bonding system; the bindingmaterial used is polyurethane resin or epoxy resin; the binder releasesat least part of the particulate material; the binder contains furtheringredients for the improvement of printability, such as, for example,an increase or decrease in viscosity and/or surface tension; theparticulate material used is a filler material.

Accordingly, pursuant to a second aspect of the present invention, thereis contemplated a process for layerwise construction ofthree-dimensional components, whereby the material comprises at leastone particulate material and a bonding agent for self-hardening of theparticulate material, with a setting time which is at least severaltimes as long as the application time of a particulate layer.

The invention of the second aspect may be further characterized by oneor any combination of the features described herein, such as the settingtime is between 20 and 150 times as long as the application time for theparticulate layer; the component demonstrates uncured setting within 72hours; the setting time is controlled by process temperature; thepolymerisation of the binder using UV light, radiation, heat and/orreactive activators is employed.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the preferred embodiment of the invention are described inrelation to the following drawings which are explained in detail.

The drawings show:

FIG. 1 a-h, illustrate a side view of the order of process of theinvention according to the preferred embodiment;

FIG. 2 a-h, illustrate the effect of different hardening speeds ondeformation;

FIG. 3 a-b, illustrate the drying of the component in a powder bed.

DETAILED DESCRIPTION

In contrast to the invention described above is a self-hardeningmaterial for layered formation of three-dimensional components, wherebythe material comprises at least one particulate material and a separatebinding material for bonding the particulate material, and a settingduration which is at least several times as long as the application timeof the particulate layer.

With such a material it is then possible that the first formedunderlying layer is only bonded and hardened after a specific period oftime. Subsequent layers do not harden until after this period haselapsed. Due to the similar time of hardening, no stress occurs in theprinted area, and therefore there is no significant warping ordeformation.

A self-hardening system in the sense of this invention is intended tomean a bonding system which, without outside influence (in the form oftemperature, energy input, etc.) that can harden within 72 hours. Thetime required is referred to as setting time.

This is not intended to mean complete hardening. A green cure issufficient in which the form of the component is stable, but cannot bearloads. This means that the components should be able to support theirown weight. A large part (>50%) of the shrinkage which takes placeduring hardening occurs during this time.

Achieving delayed hardening in the sense of the invention involvesallowing less than 5% of setting, and hence shrinkage, to occur within alayer before the next layer is deposited.

A further advantage of the invention shown here is a process for thelayered formation of three-dimensional components, whereby the materialcomprises at least one particulate material and a separate bindingmaterial for bonding the particulate material, and a setting durationwhich is at least several times as long as the application time of theparticulate layer.

As a result of setting time, commencement of setting, and delayingshrinkage, hardening of the entire piece can be made effectivelysimultaneous (relative to the overall time frame). As a consequence thecomponent shrinks overall by the same amount and at the same time, sothat no stress is developed. Any stresses developed by the small amountof shrinkage during the formation phase are relieved in the softcomponents which have yet to harden.

The uniform shrinkage can, as with casting models, be accounted forusing a scaling factor during the CAD model scaling process. If thecomponent decreases during hardening by a factor of X, the model can bemade larger by the same factor X. Process related shrinkage will thenresult in a model of the correct size.

The speed of reaction (i.e. setting) depends on the time taken todeposit a layer and dope it, and on the height of a layer. It is usuallynot necessary to delay hardening until the entire model is formed. As arule, a delay in hardening for the time it takes to build up at least 20layers is sufficient.

A particular advantage has been demonstrated if the component setswithin at least 48 hours.

The optimal value for the delay necessary for a certain component andmaterial can be determined by a person skilled in the art using a simpletrial (making and testing a sample part).

Often, a hardening delay of 150 particulate layers is sufficient.

In the preferred embodiment, however, and depending on the component andmaterial used, it can also be advantageous if the setting (i.e.solidification) only occurs after formation of the entire component.

Setting delay can be effected, for example, by lowering the temperatureduring formation.

According to a further embodiment of the present invention, it can alsobe a benefit if reaction inhibitors are added to the bonding agentand/or particulate material.

Further, a slow acting binder can be used.

With materials and processes disclosed by this invention it is nowpossible to use materials which up to now have been deemed inappropriatedue to their tendency to shrink.

Within the meaning of this invention, bonding agents and/or bindersinclude all substances that can bind the particulate material and canform a coherent structure. Various materials and reaction mechanisms areappropriate for this. Binders and particulate materials especially mustbe part of a suitable system.

Examples of appropriate materials and reaction mechanisms include thefollowing:

-   -   Monomeric binder systems based on acrylates, methacrylates,        styrols, cross-linked or not cross-linked, polymerisation        triggered by UV light, radiation, heat, reactive activators.    -   Multiple component glue systems such as polyurethane resins or        epoxy resins for which cross-linking occurs through the reaction        of two components.    -   Substances which dissolve all or part of the particulate        materials and bond them in this way.

The binding material can also contain different solvents and/ormonomers, chemicals that cause cross-linking and/or reaction assistingchemicals such as delayers, catalysts and fillers (e.g. nanoparticles).In order to improve the print characteristics, the binder liquid cancontain yet further additives e.g. for changing viscosity.

In an especially preferred embodiment of the invention, the particulatematerial contains fillers in order to minimize shrinkage of thecomponent or to improve the material's characteristics

Furthermore, additives such as initiators, catalysts and delayers can beadded to the particulate material which, for example, may be requiredfor the bonding reaction.

In an especially preferred embodiment of the process, the bonding of thegrains of the particulate material can be achieved by solvents.

A particular advantage of this in the preferred embodiment is the use ofa highly soluble plastic such as, for example, polyethylmethacrylate asthe particulate material.

The binding material can contain solvents, such as alcohols, ketones oracetates. It can also be a mixture of different solvents.

Because the binding material contains a solvent, there is no need forpreparing and dosing the binder, in order, for example, to prevent theplugging of print heads.

The bonding function of the solvent according to this preferredembodiment is based on the grains of the particulate material beingdissolved in the printed areas and bonded together. When the solventescapes, the contact surfaces of the grains are bonded and a solidregion is established. In some cases, a reduction in material can beseen.

Because setting and shrinkage are linked to the degree of thinning outof the solvent, even setting within the component can be achieved byslowing down the evaporation rate, thereby reducing deformation.

In a preferred embodiment of the process, this can be achieved throughcontrol of, and especially reduction of the process temperature.

In a further preferred embodiment of the process, one can delay thevolatilisation of alcohol through the addition of a moisture-containingmaterial such as monoethylene glycol.

A particularly beneficial solution can be achieved by varying thesolvents used. The higher alcohols (n-butanol, pentanol, hexanol, etc.),which have higher boiling points and lower steam pressure, can provide asimple and effective way to reduce evaporation.

With a process temperature of, for example, 20° C. and the use of apolyethylmethacrylate-containing particulate material, pentanol canachieve very good results when used as a solvent. In a preferredembodiment of the invention the solvent can be printed (i.e. applied)using a drop-on-demand print head onto a previously applied particulatelayer. The amount of pentanol used corresponds for example to about 9%by weight of the particulate material. Components so formed display nomeasurable deformation. The bonding of the components is greater than byother known processes. Because only a simple plastic powder and alcoholare used as reagents, the material costs are also low.

The components can be cured either in a powder bed or individually,according to readiness, at room temperature or at a specifiedtemperature.

If the components are taken out of the powder bed before curing, caremust be taken to ensure that uneven drying does not cause deformation. Acomponent can, for example, dry out in an uneven way if it is lying on anon-porous surface. The underside remains moist longer under thesecircumstances and can eventually lead to deformation during curing ofthe component.

It can therefore be advantageous for deformation free components becausethey can dry out evenly.

Furthermore, components which are still wet and delicate could bedamaged by being taken away or warp under their self weight.

In a preferred embodiment of the invention, drying takes place in such away that the component is left for a period of time in a loose powderbed and is covered with powder until it is adequately dried. One shouldtake care that the powder bed is adequately permeable for the solvent.

If the particulate material itself is able to transport the solvent, thecomponent can be dried as far as possible, or completely, in the powderbed. This allows the solvent to diffuse in the powder bed from grain tograin. It is important that the particulate material is soluble in thesolvent.

In the sense of this invention, however, the filling material can alsobe chosen such that it, at least partially, takes up and/or passes onthe solvent.

In addition, the solvent can also be chosen such that it is sufficientlytaken up and/or passed on by the filling material.

By using solvent as a binding material to bond the particulate material,only a limited strength of the components can be achieved, because afterevaporation of the solvent a porous structure remains.

In order to achieve even higher strength, according to the preferredembodiment, one can advantageously employ additional material in theform of a binder in the powder bed.

Almost all of the appropriate binders for the process demonstrate avolume reduction on setting. For example, the setting reaction ofradical-polymerised binders breaks the double bonding of the monomers,and forms a bond to the next monomer. The distance between the moleculesis reduced if they polymerise into such a macromolecule, which appearson the macroscopic level as volume reduction. With polymerisation of themonomer methylmethacrylate to polymethylmethacrylate, for example,shrinkage of 21% is observed.

In a particularly beneficial embodiment of the process, a binder basedon various methacrylates and/or styrols is used which, for example, canbe selectively laid down using a piezoelectric print head onto a powderlayer.

In addition to a monomer the binding material can also be across-linking agent (e.g. multifunctional methacrylate). A catalyst(toluidine) and/or delayer (chinon) can also be used.

Further additives and reagents are forseeable. A person skilled in theart can set the characteristics of the binding material, and thus of thecomponent, by modifying the binder makeup thus creating a targetedmaterial.

Furthermore, it is possible to add other chemicals to increase or reduceviscosity, surface tension and/or other print characteristics thatchange way the binder flows. In this way, the printability of the bindercan be improved.

In a preferred embodiment of the present invention, the particulatematerial can be a PMMA-based pearl polymer. Other materials such as ABS,PC-ABS, PA, PBT and metals could also be employed.

In addition, the particulate filler material can be glass, metals orcarbon fibre.

Beneficially, the particulate material can have reaction initiatorproperties (e.g. benzoyl peroxide). Such an initiator could either bemixed with the particulate material or be dissolved in the grains of theparticulate material.

In the preferred embodiment described, when a printing fluid with bindercharacteristics is printed onto a particulate material a chemicalreaction takes place between the initiator found in the powder (BPO) andthe catalyst (toluidine) found in the fluid. Radicals are formed whichtrigger polymerisation of the monomers.

Tests have shown that with such a system components with high strengthcan be made by a 3D printing process.

In order, however, to prevent deformation, the polymerisation reactionis delayed by the process of the invention.

The delay can be caused in various ways. Thereby, several effects can beused in order to control the reaction kinetics in such a way thatdeformation-free components can be produced.

A range of especially beneficial possibilities is described below:

-   -   The amount and type of initiator (e.g. benzoyl peroxide)        determines the speed of polymerisation. Using four times the        amount of an initiator doubles the reaction speed. Different        initiators have different decay rates and different levels of        effectiveness in starting the polymerisation reaction. A typical        amount of initiator is less than 5% of the amount of monomer        used, and 0.1 to 2% would be preferable, depending on the        monomer used.    -   Through the addition of various amounts of catalyst (e.g.        toluidine), the reaction speed can be controlled. Larger amounts        of catalyst give fast polymerisation reactions. It is favourable        to add amounts up to 5%. Better yet are additions of between 0.1        and 1%, depending on the monomer used.    -   The initiator (e.g. benzoylperoxide) can either be added with        the particulate material or be dissolved in the grains. The        polymerisation reaction is delayed if the initiator is included        in the grain, because the grain must dissolve and the initiator        must flow out before a polymerisation reaction can start. The        solubility of the particulate material, the monomer's        aggressiveness and temperature determine the speed of        dissolution.    -   An appropriate choice of monomers can be made by a person        skilled in the art to control reaction speed. Different monomers        have different reaction speeds. In addition, it is possible to        achieve an accelerated reaction through the use of a combination        of different monomers in a binding system (e.g. copolymerisation        of sterol and methylmethacrylate) in comparison to a        one-component system.    -   The temperature at which the polymerisation occurs determines        reaction speed. Higher temperatures increase the movement of        molecules. Therefore they can find their reaction partner more        quickly and polymerisation speed increases.    -   A further possibility to delay the reaction is through the use        of a substance that slows down the reaction. It is of particular        benefit to use such materials that can delay polymerisation        reactions without dampening the reactivity of the system. One        such delayer is, for example, benzochinone. Delayers, which        generally slow down a reaction, lead to the result that not all        of the monomer will be converted. Unreacted monomer is not        favourable because it causes weakening of the component. This is        not the case with delayers of the first type.

The possibilities listed above present only a selection of the choices.A person skilled in the art can tailor the reaction kinetics via theabove methods to the demands of the process.

When setting the reaction speed in the sense of this invention, caremust be taken that polymerisation takes place slowly enough that theshrinkage which occurs does not result in deformation of the component.In general this is achieved when the reaction time is greater than thetime that the 3D printer needs to form the component.

In an especially preferred embodiment of this invention, the particulatematerial is set in a thickening material which quickly takes up theliquid and increases its viscosity. This decreases the tendency ofliquid to soak into the powder bed and the geometry of the component isrendered exactly.

Of special benefit is that the thickening is achieved by the particulatematerial itself or its components. In a preferred embodiment of theinvention this is achieved by using a polymer dissolved in the printfluid that raises its viscosity. In this way, even small amounts ofpolymer powder are sufficient to thicken the fluid.

Further beneficial embodiments of this present invention are submittedin the claims below as well as their descriptions.

In relation to FIG. 1, the following describes the order of printingaccording to a preferred embodiment of the invented process usinglayerwise construction of models made of particulate material andbinding material as a rapid prototyping process.

According to the preferred embodiment described, the particulatematerial indicated is polyethylmethacrylate and the binding material is1-pentanol.

In forming a component such as, for example, a casting model, a baseplatform 4 that the model is to be built on is sized to the layerthickness of the particulate material 5. Next, particulate material 5,for example a very fine, polyethylmethacrylate-based, alcohol-solubleplastic powder is applied using a layering tool 1 onto base platform 4in the desired layer thickness. Next, the binder, for example pentanol,is selectively applied to the areas to be hardened. This can, forexample, be carried out by means of a drop-on-demand droplet generator 3of the ink jet printer type. This layering step is repeated until thefinished component, bedded in loose particulate material 5, is complete.

To start with, the layering tool 1 is in the home position, which isshown in FIG. 1 a.

As shown in FIG. 1 b, the following describes the construction of amodel with base platform 4 which is lowered by more than one layer.

Next the layering tool 1, as shown in FIG. 1 c, travels across withoutdepositing particulate material to the position opposite the fillingdevice 2, until it stands over the border of base platform 4.

Now the base platform 4 is raised to exactly the height for layering,which can be seen in FIG. 1 d. This means that base platform 4 is nowexactly one layer thickness lower than the layer height.

Finally, the layering tool 1 is driven in a constant motion over baseplatform 4. This delivers particulate material 5 in exactly the rightamount and coats base platform 4. This is shown in FIG. 1 e.

The layering tool 1 moves back after the deposition run withoutdeviation at high speed to the home position and can as needed be filledagain with the filling device 2. This is shown in FIG. 1 f.

The print head 3 now moves over base platform 4 and thereby doses thebinder selectively in the areas where hardening is desired. This isshown in FIG. 1 g.

Next, the print head 3 moves back to the home position and all elementsare back in the starting position. This is shown in FIG. 1 h, whichcorresponds to FIG. 1 a.

The printing process for the binding material on particulate material 1can be done during or after layering.

The steps 1 a to 1 h are repeated until the component, bedded in looseparticulate material, is printed to the target height.

The component is left for a sufficient amount of time in the powder beduntil adequate hardness is achieved.

Afterwards, it can be taken out and cleaned of any remaining powder.

The component can then be put through appropriate post-processes.

In relation to FIG. 2 one can see the deformation effect with differentsetting speeds. Particulate material 5 and binder are appliedalternately in a layer 6. The printed area 7 contracts resulting inshrinkage 8. In FIGS. 2 a to 2 e it is shown that over-rapid hardeningand the consequent shrinkage can lead to geometry deformation incompleted components. In the sense of this invention, this can beprevented using a targeted delay of the setting time as shown in FIGS. 2f to 2 h.

Next, a layer 6 of particulate material 5 is printed with binder in area7. This is shown in FIG. 2 a.

The printed area 7 retracts 8 as a consequence of faster fixation. Thisis shown in FIG. 2 b.

A second layer 9 of particulate material is applied and printed 7. Thisis shown in FIG. 2 c.

This now also retracts in layer 9. Because both layers are combined withone another, the force is transmitted to the underside of layer 6.

If layer 6 is set hard enough, the tension within the layers causescurvature 10. This is shown in FIG. 2 d.

The resulting component will display this curved deformation.

If the lower level is still soft, the tension is relieved throughplastic deformation 8. This is shown in FIG. 2 e.

Because this error is accumulated over many layers, the resultingcomponent has sloping sides.

Model construction from layer 6 proceeds in the same way using delayedbinding systems. However between the layers there is no hardening andtherefore no shrinkage of the printed area 7. This is shown in FIGS. 2 fand 2 g.

The hardening and shrinkage 8 is delayed until after formation of themodel. Thereby all areas of the component shrink virtually at the sametime and by the same amount. There is no deformation. This is shown inFIG. 2 h.

In relation to FIG. 3 the following describes the process for drying andsetting of a solvent-based binder according to a preferred embodiment ofthe process in this invention.

According to the preferred embodiment described, the particulatematerial is polyethylmethacrylate and the binding material is1-pentanol.

The component will, as described here, be constructed on a layered basisand, according to the preferred embodiment, the completed component,bedded in loose particulate material 5, will be left in the powder bedto dry.

In FIG. 3 a it is shown that with too large an amount of insolublefilling material in particulate material 5, drying cannot take placecompletely. Because the solvent transport from the component primarilytakes place over the contact points between particles in the printedarea and particles in the surrounding powder bed, the insolubleparticles make it more difficult for the solvent 12 to diffuse afterseveral millimetres. The powder in this area 11 is completely saturatedand cannot further absorb solvent from the component 7.

With a system using polyethylmethacrylate particulate material andpolymethylmethacrylate filling material, and a pentanol binder,saturation occurs after approximately 5 hours. The thickness of themarginal layer is about 2 mm.

If there is sufficient soluble particulate material around thecomponent, the solvent can diffuse unhindered into the material aroundit away from the component, and therefore dries. This is shown in FIG. 3b.

If a pure and soluble polyethylmethacrylate particulate material is usedwithout filler, the solvent can escape over the surrounding powder fromthe component. It dries almost completely within 24 hours.

A stronger solvent can also be used as a binder, so that even the fillerallows passage of the binder.

TABLE 1 weight- No. components percentage/[%]  (5) particle material(12) base material PMMA-beads  2-100 (13) initiator Benzoylperoxid(dissolved in base material) 0.1-5   (14) filler i.e. metal powder,glass-/carbon fiber, 5-98 insoluble polymer (22) Binder (15) monomers (15a) styrol 0-75  (15b) hydoxyethylmethacrylate 25-100 (16) Crosslinker polyethylenglykol-dimethacrylat 0-50 (17) accelerator/catalystN,N-dimethyl-p-toluidin 0.5-1.5  (18) Delayer p-benzochinon  0-0.3

Formulas

I(13)→2R*(19)  1a

R*(19)+M(15)→RM*(20)  1b

RM*(20)+nM(15)→RM _(n+1)*  1c

combination: RM _(n) *+RM _(m) *→RM _(n+m) R(21)

Disproportioning: RM _(n) *+RM _(m) *→RM _(n) +RM _(m)(21)  1d

In relation to Table 1 and Formulas 1a-1d the following shows theprocess for drying and hardening of a binder based on radicalpolymerisation solvent according to a preferred embodiment of theprocess in the invention.

A special benefit is that the particulate material can bepolymethylmethacrylate-based and the binder can be based on variousmethacrylates and/or styrols. The functioning of such a powder/liquidsystem is shown in Table 1.

The component is, as already described, to be constructed in a layeredmanner from a particulate material and a binder.

As soon as the binder from the print head meets the particulatematerial, the interactions between different parts of the system begin.

Next, the base material is dissolved 12. This causes the initiator 13 inthe base material 12 to float out of the grains. The speed of this stepis determined by the solubility of the base material 12 and the solventstrength of the binder 22. As shown in Formula 1a, the initiator 13 issplit by the accelerator 17 and forms radicals 19.

These radicals split the double bonds of monomer 15 and react withmonomer radicals 20. This is shown in Formula 1b.

The addition of further monomers 15 to the monomer radicals 20 forms amacromolecule 21. The choice and composition of the monomer 15 cancontrol the speed of the growth reaction. The growth reaction ispresented in Formula 1c.

The growth reaction is terminated by the size of the macromolecule.There are various termination mechanisms described in the literature.Formula 4e shows breaking of the chain through combination anddisproportionation.

1-17. (canceled)
 18. A self-hardening material for layerwiseconstruction of three-dimensional components, whereby the materialcomprises at least one particulate material and a separately appliedbonding agent for bonding the particulate material, and where a settingtime is at least several times as long as a application time of aparticulate layer.
 19. The self-hardening material as per claim 18,whereby the setting time is greater than 20 times as long as theapplication time of the particulate layer.
 20. The self-hardeningmaterial as per claim 18, in which setting of the binding material takesplace after formation of the component.
 21. The self-hardening materialas per claim 18, whereby the component demonstrates uncured settingwithin 72 hours.
 22. The self-hardening material as per claim 18,whereby the binder contains at least one component of the groupincluding acrylate, methacrylate and/or sterols.
 23. The self-hardeningmaterial as per claim 18, whereby the particulate material used ispolymethylmethacrylate.
 24. The self-hardening material as per claim 18,whereby the binding material can be polymerised using UV light,radiation, heat and/or reactive activators.
 25. The self-hardeningmaterial as per claim 18, whereby the binder is composed of amulti-component bonding system.
 26. The self-hardening material as perclaim 18, whereby the binding material used is polyurethane resin orepoxy resin.
 27. The self-hardening material as per claim 18, wherebythe binder releases at least part of the particulate material.
 28. Theself-hardening material as per claim 18, whereby the binder containsfurther ingredients for the improvement of printability, such as, forexample, an increase or decrease in viscosity and/or surface tension.29. The self-hardening material as per claim 18, the particulatematerial used is a filler material.
 30. A process for layerwiseconstruction of three-dimensional components, whereby a materialcomprises at least one particulate material and a bonding agent forself-hardening of a particulate material, with a setting time which isat least several times as long as a application time of a particulatelayer.
 31. The process according to claim 30, whereby the setting timeis between 20 and 150 times as long as the application time for theparticulate layer.
 32. The process according to claim 30, whereby thecomponent demonstrates uncured setting within 72 hours.
 33. The processaccording to claim 30, whereby the setting time is controlled by processtemperature.
 34. The process according to claim 30, wherebypolymerisation of the binder using UV light, radiation, heat and/orreactive activators is employed.